The present invention relates in general to dual mode WLAN/WWAN telecommunication systems, and, more specifically, to maintaining Quality of Service (QoS) in the WLAN.
Wireless local area network (WLAN) telecommunication systems are being used in many workplace/office settings as an alternative to traditional, hardwired private branch exchange (PBX) and Centrex systems. WLAN systems comprise an array of wireless access points (AP's) deployed within a building connected by a wired LAN and communicating wirelessly with telephone appliances carried by individual system users. Each access point provides a respective coverage area such that coverage areas overlap and users can maintain a constant network connection as they move (i.e., roam) throughout the building.
WLAN systems provide many benefits over wired systems such as lower installation, upgrading, and maintenance costs. They provide a wide array of telephone features, which are easy to add and modify for new and existing users. Voice calls between users of the WLAN system are free of airtime or other charges. Gateways are used to interface the WLAN system with wireless wide area network (WWAN) systems such as cellular networks and with the public switched telephone network (PSTN) for establishing voice calls between WLAN users and conventional phone customers.
In dual mode WLAN/WWAN systems, a user's phone call is carried by the WLAN while in the workplace and is then handed off to the WWAN when the user moves out of range of the WLAN. Migration of active calls between the two networks is shown, for example, by United States Publication 2002/0085516A1, entitled “Automatic and Seamless Vertical Roaming Between Wireless Local Area Network (WLAN) and Wireless Wide Area Network (WWAN) While Maintaining an Active Voice or Streaming Data Connection: Systems, Methods and Program Products”. Preferably, a single phone appliance incorporates transceivers for operating with both networks so that the handoff between the two systems is transparent to the user.
Each wireless access point connected within a WLAN has a certain throughput capacity or bandwidth. Consumption of the bandwidth depends upon the number of users associated with the AP and their level of activity at any one time. When the aggregated traffic of all users approaches the bandwidth capacity of the AP, then issues of quality of service provided to the users arises. Typical mechanisms for controlling QoS give priority to one type of traffic over another or one class of subscribers over another. For example, it is known in WLAN systems to give priority to all voice traffic over any data services being accessed over the network.
The coverage area of any particular wireless access point may include workplace areas subject to different typical uses. For example, primary workstations such as an office desk of a user may be covered as well as transient or secondary work areas for all employees in a building such as conference rooms, file rooms, lunch rooms, or others. Consequently, the priority of voice over data traffic may not always be desirable. For example, a user at their desk may be accessing a data service via a particular access point, while a voice user who is roaming enters the particular access point coverage area. It may undesirable disrupt the data traffic of the user at their desk, especially when the voice call of the roaming user could be migrated to the WWAN system.